This invention relates to an apparatus for inserting two weft threads into two warp sheds in a loom with central jet insertion, wherein a programmed weft change is being carried out.
It is known to insert two weft threads into two different warp sheds, the latter being disposed in a side-by-side relation and the inserting device, i.e. a weft metering device and picking nozzles, located intermediate the warp sheds and forming a socalled central jet inserting device. To obtain a weft change (See, for example, British patent application No. 2,079,332), the devices displace the nozzles either mechanically by rotating them through 180.degree. in order to insert the weft threads into the warp sheds in accordance with a program, in which case the device for high speed looms is expensive to manufacture and noisy, or there is used, for each of the two weft threads to be inserted, nozzles having their outlets directed into the two warp sheds; each one of the nozzles in such arrangement has its outlets directed into the two warp sheds; each nozzle has at least two pressure air feeds which can be alternately opened according to a program; such arrangement is disclosed in the British patent application No. 2,079,332. These pressure air feeds do not permit active action on the weft thread when it is changed from one warp shed into the opposite shed; since the weft threads act due to the kinetic energy of the stream only in the picking direction, changing of the direction of movement of the weft thread is caused only by negative pressure air streams; however, streams can be utilized which are produced by an ejector effect; these stream exert very low forces on the weft thread. For that reason, these devices are unreliable, particularly for higher loom speeds and heavier weft threads.